1. Field of the Invention
The present invention relates to an oil-dispersible composite of metallic nanoparticles and a method for synthesizing the same. Particularly, the oil-dispersible composite includes an oily polymeric polymer capable of chelating the metal. The oil-dispersible composite at high concentrations can be made into a film suitable for applications in electronics, sensors, antibacterial materials, nano-composites and polymers.
2. Related Prior Arts
Water is generally the solvent for producing silver nanoparticles (AgNPs). However, silver nanoparticles always gather with each other due to van der Waals' forces and it's hard for them to be dispersed in oily solvents or made in the form of powders. Therefore, it's very important to make silver nanoparticles more compatible with oily solvents in addition to controlling the particle size and stability.
To control particle sizes of the silver nanoparticles in chemical reduction processes, their thermal stability and compatible solvent phases should be considered. Therefore, organic surfactants or stabilizers are usually added to stabilize the silver nanoparticles in accordance with their electrostatic repulse or steric hindrance.
The known stabilizers include sodium polyacrylate, polyacrylamide (see J. Phys. Chem. B 1998, 102, 10663-10666), thioalkylated poly(ethylene glycol) (see Chem. Mater. 2005, 17, 4630-4635), 3-aminopropyltrimethoxysilane (APS) (see Langmuir 1999, 15, 948-951) and sodium citrate (see J. Phys. Chem. B 1999, 103, 9533-9539). The known surfactants include cationic surfactants such as cetyltrimethylammonium bromide-CTAB, anionic surfactants such as sodium dodecyl sulfate-SDS and nonionic surfactants such as ethoxylated (see Langmuir 1996, 12, 3585-3589) and poly(oxyethylene) isooctylphenyl ether-TX-100 (see Langmuir 1997, 13, 1481-1485).
To form silver paste, the solid content is required to be over 10 wt %. However, the above methods can proceed only in water phase and self-aggregation of the silver particles occurs at high solid contents. To prevent the reduced particles from aggregating, the concentrations of the silver ions must be lowered to ppm ranges during the reduction process. Moreover, the above methods require high cost because of complex processes and lengthy operations.
Therefore, the present invention provides an efficient method compatible with various solvent phases and capable of producing oil-dispersible silver nanoparticles.